Systems of Plumbing for Building Drainage

The plumbing system of a building includes the water distribution pipes, the fixture and the fixture traps, the waste, soil, and vent pipes, the building drain and building sewer, the storm drainage system with their connected devices, connections, and appurtenances within the building and outside, within the property line.     

Types of Plumbing System in Building Construction
The plumbing system installed in the building has two main objectives to be served. They are:
  1. Supply of water for the human use
  2. To get rid of human waste           
When considering systems of plumbing, there are four categories. They are:
  1. Single stack system
  2. Partially vented single stack system
  3. One-pipe system
  4. Two-pipe system

1. Single Stack System

A single stack system is the simplest form of plumbing system among the four categories mentioned. The figure-2 shows the basic arrangement of a single stack system. 

Fig.2: Single Stack System in Plumbing
S= Sink; B= Basin; L.B=Lavatory Basin; M.H=Manhole

This system of pipes carries wastewater from the wash basin, bathrooms, sinks, and foul matter from the water closets (W.C) through a single pipe called as the soil and the waste pipe (S.W.P). The pipe will terminate as the vent pipe at its top and there is no separate vent. It is the most simple and economical system as it employs a single pipe.

A single stack system will need the use of traps that are filled with a depth not less than 75mm water seal. 

2. Partially Vented Single Stack System

A partially vented single stack system is a combination of a single stack system and one pipe system. Here, the waste from the W.C., basins, sinks, etc are discharged to a common S.W.P., but a vent pipe is provided to the traps of W.C.s.

Partially Vented Single Stack System
Fig.3.Partially Vented Single Stack System

This is a single stack system where the vent pipe provides ventilation to the traps of the water closet. Here the traps of the wash basin and the sinks are not connected to the vent pipes. The figure-3 shows a partially vented single stack system.

3. One Pipe System

Here the system uses a single stack and a separate vent pipe to receive the connections from all the traps. This will not be the only trap for closets, but also for sinks, wash basins, etc. Figure -4 shows a one-pipe system.

One-Pipe System
Fig.4: One-Pipe System

In a multistoried building, the lavatory blocks of different floors are situated one above the other, so that discharge from various units at different floors can be carried through common soil and waste pipe (S.W.P.). The system is costlier than the single-stack system.

4. Two Pipe System

The two-pipe plumbing system will make use of separate pipes for connecting the water closets and for the discharges from the basin, baths, sinks, etc. i.e separate soil pipe (S.P.) and waste pipe (W.P.). 

The discharge from W.C. goes to the S.P., while the discharge from baths, sinks, and lavatory goes to the W.P...

Fig.5: Two-pipe system

Here both pipes are separately ventilated by different vent pipes as shown above. A gully trap is used to disconnect the discharge from the waste pipe from the drain. This system forms a four-pipe connection system (Figure 5). Most multistoried buildings prefer this system. 

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